JP2013134490A - Method for manufacturing electrophotographic photoreceptor and electrophotographic photoreceptor manufactured by manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a high-quality electrophotographic photoreceptor for suppressing scattering of a coating liquid in an immersion coating process even when a coating liquid with a low viscosity is used, and to provide an electrophotographic photoreceptor manufactured by the manufacturing method.SOLUTION: The method includes an immersion step and a formation step. In the immersion step, a cylindrical substrate with one end closed and the other end opened is immersed from the opened other end side in a coating liquid having a viscosity of 50 mPa s or lower. In the formation step, the immersed substrate is pulled up from the coating liquid to form a coating layer comprising the coating liquid on an outer circumferential surface of the substrate. In a period when the other end of the substrate is above the liquid surface of the coating liquid and in contact with a part of the coating liquid by the surface tension of the coating liquid, air inside the substrate is evacuated from the closed one end side of the substrate.

Description

  The present invention relates to a production method for producing an electrophotographic photoreceptor suitably used in an electrophotographic image forming apparatus, and an electrophotographic photoreceptor produced by the production method.

  An electrophotographic photosensitive member used in an electrophotographic image forming apparatus has a photosensitive layer made of an organic photoconductive material formed on the outer peripheral surface of a hollow cylindrical conductive substrate. Many electrophotographic photoreceptors have been developed in response to demands for higher performance. As a result, they have an intermediate layer, charge generation layer, and charge transport layer, and some photoreceptors have improved durability. A function-separated type photoreceptor having a photosensitive layer having a laminated structure in which protective layers are sequentially formed is put into practical use.

  A thin photosensitive layer is applied with high thickness uniformity to achieve high functionality, and at the same time, an application method is being studied to enable application at low cost. As a method for applying a photosensitive layer to the outer peripheral surface of an electrophotographic photosensitive member tube serving as a conductive substrate, spray coating, dip coating, blade coating, roll coating, and the like are conventionally known. Among them, the dip coating method is the most frequently used method because of its high production efficiency.

  In the production of a photoconductor by the dip coating method, a coating solution tank is formed from the open end to the depth of the portion where the photosensitive layer is to be formed, with one end of the cylindrical object being closed and the other end open. The object to be coated is immersed in the coating solution contained in the substrate, and then the substrate is pulled up to apply the coating solution on the surface of the object to be coated to form a photoreceptor layer.

Here, when an application layer is formed on the surface of an object to be applied by a dip coating method, the relationship between the thickness of the application layer and the physical properties of the application liquid is expressed by the following formula (1).
h = K (ηV) ⁿ (1)
(Where h: coating layer thickness, η: coating solution viscosity, V: coating speed, K: constant, n: constant)

Here, the coating speed V is a relative movement speed of the coating liquid with respect to the surface of the object to be coated. The coating speed V is one in the coating liquid tank in which the circulation equipment is not incorporated so that the coating liquid is supplied or circulated, or the circulation equipment is incorporated but the supply and circulation are temporarily stopped. In the case where the object to be coated is immersed, since the surface of the coating liquid is lowered at the time of raising the volume of the object to be coated out of the coating liquid with the lifting of the coating object, the size of the coating liquid tank, It is determined by the size of the object to be coated and the pulling speed that is the speed of pulling up the object to be coated, and is represented by the following formula (2).
V = S × B ² / (B ² −A ² ) (2)
(However, S: Pull-up speed, A: Outer diameter of workpiece, B: Inner diameter of cylindrical coating liquid tank)

  On the other hand, in a coating apparatus in which a circulation facility is incorporated and the coating solution is constantly supplied or circulated, a sufficient amount of coating solution that is greater than or equal to the volume of the object to be coated out of the coating solution is constantly supplied. Since there is no drop in the coating liquid level associated with the lifting of the object to be coated, the coating speed matches the pulling speed.

  According to Formula (1), the thickness h of the coating layer is controlled by the coating speed V and the viscosity η of the coating solution. Specifically, when the thickness h of the coating layer is reduced, it is achieved by reducing at least one of the coating speed V and the viscosity η of the coating solution. Conversely, when the thickness h of the coating layer is increased, it is achieved by increasing at least one of the coating speed V and the viscosity η of the coating solution. The coating speed V is changed not only by changing the pulling speed S of the coating object, but also by changing the outer diameter A of the coating object and the inner diameter B of the coating liquid tank, as shown in the equation (2). be able to. For example, even if the pulling speed S is the same, the coating speed V decreases if the outer diameter A of the object to be coated is small, and the coating speed V increases if the outer diameter A of the object to be coated is large. If the inner diameter B of the coating solution tank is large, the coating speed V is small, and if the inner diameter B is small, the coating speed V is large.

  The viscosity of the coating solution can be changed by changing the composition of the coating solution, for example, changing the blending ratio of the organic photoconductive material and the binder resin, or using a binder resin having a different molecular weight. Can do. Specifically, if the blending ratio of the organic photoconductive material is increased, the viscosity of the coating liquid is decreased, and if the blending ratio of the binder resin is increased, the viscosity of the coating liquid is increased. Further, if a binder resin having a low molecular weight is selected, the viscosity of the coating solution is lowered, and if a binder resin having a high molecular weight is selected, the viscosity of the coating solution is increased.

  However, since the compounding ratio of the organic photoconductive material and the binder resin and the type of the binder resin affect the sensitivity, responsiveness, mechanical strength, etc. of the photoreceptor, the organic photoconductive material is usually used. The viscosity is adjusted by changing the mixing ratio of the solid content containing the binder resin and the solvent. Specifically, when the solid content concentration is increased, the viscosity of the coating solution is increased.

  In the dip coating method, the coating speed and the viscosity of the coating solution are thus set, and the thickness of the coating layer is adjusted to a predetermined preferable thickness. However, even if the coating speed and the viscosity of the coating solution are set in this way, the gas in the coating object is expanded due to a slight temperature difference between the coating solution and the outside air, and the gas is caused by evaporation of the solvent in the coating solution. In many cases, bubbles are generated from the open end due to an increase in the volume of the gas inside the object to be blocked due to the occurrence of bubbles, etc. The surface of the coating liquid sways and the coating speed changes, making it difficult to form a coating layer having a desired thickness. In addition, the amount of bubbles generated is not always constant, and the coating speed changes during the pulling up, resulting in unevenness in the coating surface of the object to be coated, which hinders the formation of a uniform coating layer.

  Therefore, a method for preventing the generation of bubbles due to an increase in the volume of gas inside the object to be coated has been proposed. In Patent Document 1, the object to be coated is immersed in the coating liquid from the open side in a state where air is blocked in the object to be coated, and immediately before the open side end portion and the coating liquid surface are separated when being pulled up. There has been proposed a method for releasing the air inside the object to be coated.

  According to the dip coating method described in Patent Document 1, bubbles are generated or applied from the open side end by releasing the air inside the object to be coated immediately before the open side end and the coating liquid surface are separated. Disturbance of the liquid level is eliminated to prevent uneven coating.

  In the method described in Patent Document 1, a thin film of the coating solution may be formed so as to close the open end when the coating solution is pulled up. The coating liquid film at the lower end may repel due to the evaporation of the solvent over time, and when the coating liquid film bounces, the coating liquid forming the coating liquid film scatters around the object to be coated. It will be.

  In recent image forming apparatuses, the size of a mounted photoconductor tends to be reduced for speeding up and downsizing, and as many coating objects as possible are immersed in one coating solution tank at a time. It has been demanded that the production efficiency of the photoreceptor is further improved by applying the coating. When a coating layer is formed by immersing a plurality of objects to be coated in one coating solution tank as described above, the scattering of the coating solution film causes the following problems.

  If the distance between adjacent objects to be coated is small, splashes of the scattered coating liquid adhere to the coating layer formed on the other objects to be coated, and the appearance quality of the electrophotographic photoreceptor as a product is deteriorated. A malfunction occurs. Further, the spray of the coating liquid as described above may reach the vicinity of the center in the axial direction of the coated object whose axial direction is kept vertical, and there is a concern about the influence on the output image when used as a photoconductor. The

  The problem that the coating liquid scatters may occur each time the undercoat layer, the charge generation layer, and the charge transport layer are formed by the dip coating method. When scattering occurs in each layer formation and the defects increase synergistically, the uniformity of the electrical characteristics and mechanical characteristics of the photoreceptor is lowered, which may cause serious defects in the output image.

  In order to solve such a problem, there has been proposed a dip coating apparatus and a coating method capable of simultaneously dip-coating a plurality of objects to be coated and reducing the influence of scattered coating liquid. The dip coating apparatus described in Patent Document 2 eliminates the coating liquid film from scattering and adhering to the adjacent coated object by setting the interval between the adjacent coated objects to 20 mm or more, and is uniform. It is said that a coating layer can be formed. Further, in Patent Document 3, when the object to be coated is pulled up from the coating liquid tank containing the coating liquid, the air inside the object to be coated is blocked when the open end and the surface of the coating liquid are separated from each other. A method is described in which, by sucking from the end portion, the coating liquid film formed on the open side end portion is sucked together with the air inside the object to be coated, and splashing around the object to be coated is prevented.

Japanese Patent Laid-Open No. 2003-140367 JP-A-6-262113 JP 2006-337759 A

  As mentioned above, several production methods have been proposed to increase the production efficiency and quality of electrophotographic photoreceptors. However, while maintaining the high production efficiency that is the merit of the dip coating method, high appearance quality and output It is not yet sufficient to produce an electrophotographic photoreceptor with image quality.

  For example, the dip coating apparatus described in Patent Document 2 is not proposed to reduce the scattering of the coating liquid that has formed the coating liquid film formed on the open side of the object to be coated, but is scattered. As a premise, the interval between the coated objects is set to be long so that the coating liquid does not adhere to the adjacent coated objects. That is, the problem that the coating liquid splashes is not fundamentally solved. In addition, by setting the distance between the objects to be coated to be long, the number of objects to be coated that can be processed at a time is reduced, and problems such as an increase in the size of the dip coating apparatus itself occur.

  In addition, the manufacturing method described in Patent Document 3 is effective when the coating liquid film formed on the open-side end portion is stably present, but depending on the composition of the coating solution, the open-side end portion is applied. The coating liquid film scatters as soon as it is separated from the liquid surface, and when the air inside the coating object is sucked, it is already after the coating liquid film scatters. Defects due to the spray adhesion may not be improved. In particular, in a coating solution having a low viscosity, such as a thin undercoat layer or a charge generation layer, the coating solution film formed on the open side end portion cannot exist stably. I can hardly expect.

  An object of the present invention is to provide a production method capable of producing a high-quality electrophotographic photosensitive member by suppressing scattering of the coating solution, even when a low-viscosity coating solution is used in the dip coating method, and the production method thereof The electrophotographic photosensitive member manufactured by the method is provided.

The present invention includes a dipping step in which a cylindrical substrate is immersed from the opened end side into a coating solution having a viscosity of 50 mPa · s or less with one end closed and the other end opened.
A forming step of forming a coating layer made of the coating solution on the outer peripheral surface of the substrate by pulling up the immersed substrate from the coating solution, wherein the other end of the substrate is above the liquid level of the coating solution. And a step of sucking air inside the substrate from the closed one end side during a period in which the other end of the substrate is in contact with a part of the coating solution due to the surface tension of the coating solution. And an electrophotographic photosensitive member manufacturing method.
In the present invention, the viscosity of the coating solution is 20 mPa · s or less.

  In the invention, it is preferable that the period of the forming step is a period in which the distance between the other end of the substrate and the liquid surface of the coating liquid is 0 to 5 mm.

  The present invention is characterized in that during the period of the forming step, the pulling of the substrate is interrupted for 1 to 10 seconds, and the suction is performed during the interruption.

The present invention also provides a cylindrical substrate,
An electrophotographic photoreceptor comprising: a photosensitive layer obtained by drying a coating layer formed on the outer peripheral surface of a substrate by the method for producing an electrophotographic photoreceptor described above.

  According to the present invention, in the dipping step, the cylindrical substrate is dipped from the opened other end side into a coating solution having a viscosity of 50 mPa · s or less with one end closed and the other end opened. Let The forming step is a forming step of forming a coating layer made of the coating solution on the outer peripheral surface of the substrate by pulling up the immersed substrate from the coating solution, wherein the other end of the substrate is more than the liquid level of the coating solution. In the period above which the other end of the substrate and a part of the coating solution are in contact with each other due to the surface tension of the coating solution, air inside the substrate is sucked from the closed one end side.

  As a result, by sucking the inside of the substrate during the period as described above, even when a coating solution having a low viscosity is used, scattering of the coating solution can be suppressed and a high-quality electrophotographic photosensitive member can be produced. .

  Moreover, according to this invention, even if it is a case where the coating liquid of very low viscosity is used so that the viscosity of the said coating liquid is 20 mPa * s or less, scattering of a coating liquid can be suppressed.

  Moreover, according to this invention, scattering of a coating liquid can be reliably suppressed by attracting | sucking in the period when the distance of the other end of a base | substrate and the liquid level of a coating liquid is 0-5 mm.

  According to the invention, during the period of the forming step, the pulling of the substrate is interrupted for 1 to 10 seconds, and the suction is performed during the interruption. When the pulling speed is high, the suction period is shortened. Therefore, the period can be extended by the interruption time by interrupting the pulling of the substrate, and the suction can be performed even when the pulling speed is high.

  According to the invention, the electrophotographic photosensitive member comprises a cylindrical substrate, and a photosensitive layer obtained by drying the coating layer formed on the outer peripheral surface of the substrate by the method for producing an electrophotographic photosensitive member. Therefore, the photosensitive layer is free from defects and high-quality image formation can be performed.

It is a side view which simplifies and shows the structure of the dip coating apparatus. It is a figure explaining the outline | summary of the manufacturing method of the electrophotographic photoreceptor which is embodiment of this invention. It is the schematic diagram which showed the state of the coating liquid surface 13a when pulling up the to-be-coated object 12 from the coating liquid 13 in steps. FIG. 2 is a cross-sectional view illustrating a configuration of a multilayer electrophotographic photosensitive member. It is sectional drawing which shows the structure of a single layer type electrophotographic photoreceptor.

  The method for producing an electrophotographic photosensitive member according to the present invention is a cylindrical substrate having one end closed and the other end opened to a coating solution having a viscosity of 50 mPa · s or less. A dipping step of dipping from the end side, and a forming step of forming a photosensitive layer made of the coating solution on the outer peripheral surface of the substrate by pulling up the dipped substrate from the coating solution. During the period when the end is above the liquid surface of the coating solution and the other end of the substrate is in contact with a part of the coating solution due to the surface tension of the coating solution, the air inside the substrate from the closed one end And a forming step of sucking the liquid.

  In this embodiment, when the undercoat layer, the charge generation layer, and the charge transport layer are each referred to as a photosensitive layer, all the layers may be collectively referred to as a photosensitive layer.

  Below, the dip coating apparatus used suitably for the manufacturing method of this invention is demonstrated first, and the manufacturing method of an electrophotographic photoreceptor is demonstrated in detail after that.

  FIG. 1 is a side view showing a simplified configuration of the dip coating apparatus 11. The dip coating apparatus 11 binds materials such as an organic photoconductive material for constituting the photosensitive layer, for example, a charge generating substance for constituting the charge generating layer, a charge transporting substance for constituting the charge transporting layer. A coating solution for a photosensitive layer dissolved or dispersed in a solvent such as an organic solvent together with a resin is applied to the outer peripheral surface of the conductive substrate or another layer formed on the conductive substrate to form a coating solution layer. . The types of the conductive substrate and the coating solution will be described later.

  The dip coating apparatus 11 contains a coating solution 13 containing components of a photosensitive layer to be formed on the coating object 12, a coating solution tank 14 in which a plurality of coating objects 12 are immersed, and a cylindrical coating object 12. The gripping device 15 that holds the one end 12a vertically upward and closes and grips the one end 12a, and the workpiece 12 gripped by the gripping device 15 vertically above and below the coating liquid tank 14 And an elevating device 16 that is moved to the inside, and a circulation device 19 that circulates the coating liquid 13 in the coating liquid tank 14 including a supply pipe 17 and a reflux pipe 18.

  The object to be coated 12 is an object to which a coating liquid 13 stored in a coating liquid tank 14 to be described later is applied, and a conductive substrate on which a photosensitive layer is not formed or another photosensitive layer is already formed. It is a conductive substrate. The object to be coated 12 is formed in a cylindrical shape, one end 12a is closed and supported by the gripping device 15, and the other end 12b is opened. The coating object 12 is immersed in the coating liquid 13 stored in the coating liquid tank 14 and pulled up, whereby the coating liquid 13 in the coating liquid tank 14 adheres to the surface of the coating object 12, and the coating liquid layer is formed. It is formed. A plurality of objects to be coated 12 are immersed in the coating solution tank 14 at the same time.

  The coating solution tank 14 is a container for storing the coating solution 13 containing the components of the photosensitive layer to be formed on the coating object 12 and immersing the coating material 12 in the coating solution 13. The coating liquid tank 14 has a size that allows the plurality of objects to be coated 12 to be adjacent to each other with a spacing d by the gripping device 15 and can immerse, for example, 40 objects to be coated simultaneously. An overflow tank 20 for temporarily storing the coating liquid 13 overflowing from the coating liquid tank 14 by immersing a plurality of objects to be coated 12 is provided on the upper part of the coating liquid tank 14.

  The gripping device 15 causes the one end 12a of the cylindrical object 12 to be vertically upward and closes the one end 12a, so that the axis of the object 12 is the liquid surface 13a of the application liquid 13 (hereinafter referred to as the liquid surface 13a). The coating liquid 13 is prevented from entering the coating object 12 while the coating object 12 is immersed in the coating liquid 13. As the gripping device 15, for example, a balloon chuck, an O-ring chuck, a mechanical chuck, or the like can be used. The gripping device 15 is provided with a number equal to or greater than the number of the objects to be coated 12 immersed in the coating liquid tank 14, and the plurality of gripping devices 15 are arranged so that the distance between the adjacent objects to be coated 12 is d. All the objects to be coated 12 are provided so that the positions of the end portions 12b on the open side are the same.

  The gripping device 15 is provided with suction means 21 for sucking air inside the object to be coated 12 from one end portion 12a on the side where the object to be coated 12 is closed. During the pulling up, the suction means 21 is inside the coating object 12 during a period in which the other end portion 12b on the side of the coating object 12 to be opened and the coating liquid surface 13a are in contact and connected by the surface tension of the coating liquid 13. Aspirate the air. The period during which the suction means 21 performs the suction operation is detected by the control means 22 described later.

  As the suction means 21, for example, one including a suction pump and an air vent valve can be used. The suction means 21 opens the air vent valve to suck the air inside the workpiece 12. The timing and the suction time for starting the suction of the air inside the object to be coated 12 by the suction means 21 are controlled by the control means 22 for controlling the operation of the entire apparatus, details of which will be described later.

  The elevating device 16 includes a male screw member 24 that is rotatably supported by the bearing 23 and extends in the vertical direction, a female screw member 25 that is screwed into the male screw member 24, and a female screw member that is inserted into the male screw member 24. A holding member 26 fixed on the holding member 25; a support member 27 having one end fixed to the holding member 26 and extending in the horizontal direction; and supporting a plurality of gripping devices 15 that grip the workpiece 12; , And a gear train 29 that transmits the rotational driving force of the motor 28 to the male screw member 24. Although one or more pairs of lifting devices 16 are provided opposite to each other with the coating solution tank 14 interposed therebetween, only one lifting device 16 is illustrated in FIG. The rotational driving force of the motor 28 is transmitted to the male screw member 24 by the gear train 29 to rotate the male screw member 24, and the female screw member 25 screwed into the male screw member 24 moves in the direction of the arrow 30. Due to the movement of the female screw member 25, the support body 27 mounted on the female screw member 25 moves upward and downward in the vertical direction, and the workpiece 12 gripped by the gripping device 15 as the support body 27 moves moves the arrow 30. Move in the direction. When the object 12 is immersed in the coating liquid tank 14, the motor 28 is rotated so that the support 27 is lowered, and when the object 12 is pulled up from the coating liquid tank 14, the case where the motor 28 is lowered. The support 27 is raised by rotating in the reverse direction. The raising / lowering speed of the support 27 by the rotation of the motor 28 is controlled by the control means 22. In addition, the position of the other end 12b on the open side of the workpiece 12 supported by the support body 27 that moves up and down by the rotation of the motor 28 via the gripping device 15 is detected by a position detection means (not shown). The detection result by the means is input to the control means 22.

  Of the lifting / lowering speed of the support 27, that is, the lifting / lowering speed of the object 12 to be immersed in the coating liquid tank 14, the pulling speed, which is the speed for lifting the object 12 from the coating liquid tank 14, is This affects the thickness of the coating layer to be formed. Such a pulling speed is set according to the thickness of the coating liquid layer to be formed. The pulling speed is preferably in the range of 1.0 to 10.0 mm / s, for example, although it depends on the size of the coating liquid tank 14 and the size of the distance d between the objects to be coated 12. If the pulling speed is less than 1.0 mm / s, the pulling speed becomes too slow, the production efficiency does not increase, and the coating liquid layer may not be formed. On the other hand, if the pulling speed exceeds 10.0 mm / s, it becomes difficult to form a thin coating layer, and coating unevenness due to large shaking of the coating solution tends to occur.

  The circulation device 19 includes a stirring tank 31 for storing the coating liquid 13 collected from the overflow tank 20, one end connected to the coating liquid tank 14, and the other end connected to the stirring tank 31. A supply pipe 17 for feeding the stored coating liquid 13 to the coating liquid tank 14, and a coating liquid stored in the overflow tank 20 with one end connected to the overflow tank 20 and the other end connected to the stirring tank 31. A reflux pipe 18 for collecting and circulating 13 in the stirring tank 31, a stirring blade 33 provided inside the stirring tank 31 and rotated by the rotation of the motor 32 to stir the coating solution 13 in the stirring tank 31; Viscosity measuring means 34 for measuring the viscosity of the coating liquid 13 stored in the stirring tank 31, and the viscosity measured by the viscosity measuring means 34 due to evaporation of the solvent in the coating liquid 13 is higher than a predetermined reference value. Na When configured to include an additional supplying solvent supply means 35 and the solvent to the stirring tank 31. In addition, the stirring tank 31 may be provided with a coating liquid dispersing device such as an ultrasonic generator in order to stabilize the dispersibility of the coating liquid 13.

  The supply pipe 17 is provided with a circulation pump 36 and a filter 38 provided on the downstream side of the circulation pump 36 in the direction of the arrow 37 that is the supply direction of the coating liquid 13 of the supply pipe 17. The circulation pump 36 feeds the coating liquid 13 stored in the stirring tank 31 to the coating liquid tank 14 side. The filter 38 removes foreign matters such as metal powder contained in the coating liquid 13 flowing through the supply pipe 17.

  According to the circulation device 19, the coating liquid 13 overflowing from the coating liquid tank 14 is collected and stored in the stirring tank 31 by the reflux pipe 18 connected to the overflow tank 20. In the stirring tank 31, the coating liquid 13 is stirred by the stirring blade 33 and the viscosity is measured by the viscosity measuring unit 34. The viscosity measured by the viscosity measuring means 34 is input to a control unit (not shown) provided in the solvent supply means 35. When the measured viscosity value is higher than a predetermined value, the solvent supply means is used to lower the viscosity. A solvent is supplied from 35 to the stirring tank 31. As a result, the coating liquid 13 in the stirring tank 31 is always maintained at a constant and suitable viscosity. The coating liquid 13 stirred in the stirring tank 31 flows through the supply pipe 17 by the circulation pump 36 and is returned to the coating liquid tank 14. At that time, the coating liquid 13 removes foreign matters by the filter 38. Thus, by circulating the coating liquid 13 between the coating liquid tank 14 and the stirring tank 31, the viscosity of the coating liquid 13 accommodated in the coating liquid tank 14 and the position of the coating liquid surface 13a are always kept constant. Is done.

  The position of the liquid level 13a of the coating liquid 13 accommodated in the coating liquid tank 14 is detected by a liquid level detection means (not shown), and the detection output by the liquid level detection means is input to the control means 22. The circulation device 19 can be stopped when the workpiece 12 is immersed and pulled, or can be always operated. In the case of always operating, the coating liquid level is lowered even during the pulling up by supplying the coating liquid amount by the circulating pump 36 to compensate for the volume decrease of the coating liquid 13 in the coating tank 14 accompanying the pulling up of the article 12 to be coated. Therefore, the pulling speed can be increased and the production efficiency can be increased.

  The position of the liquid level in the present invention is a position detected at a place away from the place where the article to be coated 12 is immersed, for example, a local liquid level that fluctuates due to immersion and pulling up of the article 12 to be coated. Is not the position.

  As a means for detecting the position of the liquid level, a general liquid level gauge can be used. As the liquid level gauge, there are, for example, a float metal tube type, a balance weight type, a round glass type, and the like. In the following, the liquid level position detecting means of the present invention will be described taking a float metal tube type liquid level gauge as an example.

The liquid level position detecting means is composed of a metal cylinder (chamber) and a magnet built-in float inserted therein. The chamber has a built-in indicator that displays the position of the float in response to the float magnet, and a part of the chamber is made of glass so that the indicator can be visually confirmed. At the top and bottom of the chamber, flanges are provided for installation in the target coating solution tank 14 so that the lower flange is at a position below the liquid level and the upper flange is at a position sufficiently above the liquid level. It is installed on the wall of the coating solution tank 14. After the installation, the inside of the chamber and the inside of the coating solution tank 14 are connected. Therefore, when the coating liquid is introduced into the coating liquid tank 14, the coating liquid is also introduced into the chamber from the lower flange, the float in the chamber rises as the liquid level rises, and the position of the float is displayed on the display. Is displayed. Since the liquid level position in the chamber coincides with the liquid level position of the coating liquid tank 14, the position of the liquid level can be detected from the float position indicated on the display.
By using such detection means, it is possible to detect the position of the liquid level without being affected by local fluctuations in the liquid level due to the immersion and pulling up of the workpiece 12.

  As described above, the control means 22 receives the detection result from each detection means for detecting the position of the open end 12b of the article 12 and the position of the coating liquid surface 13a stored in the coating liquid tank 14. Entered. The control means 22 is provided with time measuring means for measuring time. As the time measuring means, for example, means for measuring time according to the frequency of the commercial power source can be used. The control means 22 is configured so that the position of the other end 12b on the open side of the object 12 to be detected is equal to the position of the coating liquid surface 13a stored in the coating liquid tank 14 while the object 12 is being pulled up. The suction means 21 is controlled so that the air inside the coating object 12 is sucked from the starting point to a period until the other end portion 12b on the open side of the coating object 12 increases a predetermined distance. To do. Alternatively, when the predetermined distance is pulled up, the pulling is interrupted and the suction means 21 is controlled so as to suck the air in the article 12 to be coated.

  The control means 22 starts from the time when the position of the other end portion 12b on the open side of the object to be coated 12 is equal to the position of the coating liquid surface 13a, while the other end on the open side of the object to be coated 12 is being pulled up. The suction means 21 is controlled so as to suck the air inside the object to be coated 12 during the period in which the portion 12b and the coating liquid surface 13a are connected by contact with the surface tension of the coating liquid 13.

  The suction operation is more preferably performed while the distance between the other end 12b on the open side of the object to be coated 12 and the coating liquid surface 13a is 0 to 5 mm (greater than 0 mm and 5 mm or less). When the distance between the other end 12b on the open side of the object to be coated 12 and the coating liquid surface 13a is 0 mm or less, the other end 12b on the open side of the object to be coated 12 is substantially in the coating liquid 13. Therefore, the coating liquid is sucked in by suction, and the inside of the coating object 12 and the suction device may be contaminated by the coating liquid 13. The distance at which the open end 12b and the coating liquid surface can be maintained is different depending on the type of the coating liquid, but tends to be shorter as the viscosity is lower. Therefore, in the present invention, scattering of the coating liquid can be effectively suppressed by performing suction during a period until the distance between the open-side end portion 12b and the coating liquid surface 13a is at most 5 mm.

Below, the manufacturing method of the electrophotographic photoreceptor using the dip coating apparatus 11 is demonstrated.
As described above, the method for producing an electrophotographic photosensitive member of the present invention includes a dipping process and a forming process, and the forming process includes a pulling process and a suction process.

  FIG. 2 is a diagram for explaining an outline of a method for producing an electrophotographic photosensitive member according to an embodiment of the present invention. First, in the dipping process, the motor 28 is rotated to lower the support 27 that supports the workpiece 12 gripped by the gripping device 15, and the coating liquid 13 is filled as shown in FIG. The object to be coated 12 is immersed in the liquid tank 14. At this time, one end 12a of the object 12 to be coated held by the gripping device 15 is closed by the gripping device 15, and the object 12 is immersed in the coating liquid 13 from the other end 12b on the open side. . As shown in FIG. 2B, the object to be coated 12 is immersed to a depth where a photosensitive layer is desired to be formed. At this time, the air existing inside the object to be coated 12 is blocked between the one end portion 12a and the coating liquid surface in the vicinity of the other end portion 12b. The immersion of the article to be coated 12 is temporarily stopped in this state and then subjected to a pulling process. In addition, the time which the to-be-coated article 12 is immersed and temporarily stopped is, for example, about 1.0 to 30.0 seconds.

  In the pulling process, the motor 28 is rotated in the opposite direction to that in the dipping process to raise the support 27 that supports the object 12 to be gripped by the gripping device 15, and the object 12 is removed from the coating liquid 13. Pull up. By this pulling up, the coating layer 39 is formed on the workpiece 12.

  Here, the suction process of the present invention will be described in more detail with reference to FIG. FIG. 3 is a schematic diagram showing stepwise the state of the coating liquid surface 13a when the workpiece 12 is pulled up from the coating liquid 13. FIG. 3A is a stage in the middle of the application object 12 being pulled up from the coating liquid 13, and corresponds to FIG. Next, the pulling-up proceeds, and in FIG. 3B, the other end portion 12b on the open side of the workpiece 12 and the coating liquid surface 13a coincide. When the pulling is further advanced, as shown in FIG. 3C, the other end portion 12b on the open side of the object to be coated 12 is above the coating liquid surface 13a, but is released by the surface tension of the coating liquid 13. This is a period in which the other end portion 12b on the side and the surface layer portion 13b closest to the other end portion 12b, which is a part of the coating liquid 13, are in contact with each other.

  As this connection portion is further pulled up, as shown in FIG. 3D, the coating liquid film 13c is incomplete but between the other end 12b on the open side and the axis of the article 12 to be coated. Will be formed. The coating liquid film 13c at this time can exist stably because it is connected to both the other end portion 12b on the open side of the workpiece 12 and the coating liquid surface 13a. Thereafter, the pulling-up proceeds, and as shown in FIG. 3 (e), the connection between the other end 12b and the coating liquid surface 13a is completely broken, and the coating liquid film 40 is formed only on the other end 12b. Become.

  In the manufacturing method in which a plurality of objects to be coated 12 are immersed in one coating liquid tank 14, the coating liquid film 40 is repelled and the coating liquid 13 scatters, whereby the coating layer 42 formed on the adjacent objects to be coated 41. Will be contaminated by the splashed coating liquid 13. In order to suppress such scattering of the coating liquid, a suction process is performed. However, in a low-viscosity coating liquid of 50 mPa · s or less, the coating liquid film cannot exist for a long time, and is quickly scattered. And often cannot be sucked. Therefore, in the suction process of the present invention, the other end portion 12b on the open side of the object 12 is applied to the coating liquid 13 as shown in FIGS. 3 (c) and 3 (d) from FIG. When pulled up from the inside, a period in which the other end 12b on the open side and the coating liquid surface 13a are connected by the surface tension of the coating liquid, that is, the coating liquid film is completely formed on the other end 12b on the open side. Suction before it ends.

  In the suction process, the air inside the workpiece 12 is sucked by the suction means 21 from the one end portion 12a on the closed side. The suction step may be performed while pulling up the workpiece 12 or may be performed while the pulling is interrupted. In the case of interruption, it is preferable that the suction step is performed in 1 to 10 seconds after interruption. Since the suction process of the present invention is carried out immediately above the coating liquid surface 13a, if it exceeds 10 seconds, the solvent vapor of the coating liquid 13 affects the thickness of the coating layer under the object to be coated or leads to uneven coating. If the interruption period is less than 1 second, when the application speed is high, the period during which suction is possible is short, and there is a risk of placing a large load on the control of the suction device.

  In the suction step, as shown in FIG. 2 (d), the air inside the object to be coated 12 is sucked in the direction of the arrow 21a, so that when the object to be coated 12 is pulled up, the other end 12b on the open side and the coating are applied. The coating liquid film 40 that is stably generated between the liquid surface 13 a and the liquid surface 13 a is sucked into the object to be coated 12. By sucking the coating liquid film 40 into the coating object 12 in this way, an unstable coating liquid film is prevented from being formed at the other end 12b on the open side, and scattering of the coating liquid is applied. The inside of the article 12 and the open end 12b as indicated by the arrow 43 are changed to the side toward the coating liquid surface 13a, and the splashed coating liquid splash 43 is sucked into the inside of the article 12 to be coated. it can. As a result, even when a low-viscosity coating liquid in which an unstable coating liquid film 40 is easily formed is used, the coating liquid does not scatter and adheres to the coating layer 42 formed on the adjacent object 41 to be coated. Can be prevented.

  The timing at which the air inside the coating object 12 is sucked by the suction means 21 is controlled by the control means 22 as described above, and the distance between the other end 12b on the open side of the coating object 12 and the coating liquid surface 13a is zero. It is particularly preferable to carry out during a period of ˜5 mm. Moreover, it is preferable that the time for sucking the air inside the workpiece 12 by the suction means 21 is longer than 0 seconds and shorter than 5 seconds.

  When the coating layer 39 is formed on the outer peripheral surface of the workpiece 12 in this way, it is included in the coating layer 39 by at least natural drying or by forced drying by heating means such as hot air and far infrared rays. The necessary solvent is sequentially formed to complete the production of the electrophotographic photosensitive member. In addition, when using a heating means for drying of the coating layer 39, it is preferable to perform drying for 10 minutes-2 hours, for example at the temperature of 40-130 degreeC.

  As described above, according to the manufacturing method of the present invention, in the forming step, when the immersed article 12 is pulled up, the coating liquid film is formed between the other end 12b on the open side and the coating liquid surface 13a. Since the suction can be performed during a period in which 40 is stably present, it is possible to prevent the droplet 43 of the coating liquid from adhering to the coating layer 42 formed on the workpiece 41 disposed adjacent to the coating layer 41. Can do. As a result, even when a low-viscosity coating solution is used, the quality of the produced electrophotographic photosensitive member can be maintained high.

  The coating solution 13 used in the present invention has a low viscosity of 50 mPa · s or less. With this viscosity, the coating liquid film 40 formed on the other end 12b on the open side of the article to be coated 12 cannot stably exist. Therefore, after the coating liquid film 40 is completely formed, that is, the coating liquid film 40. However, since the suction after the separation from the coating liquid surface 13a is not in time, the effect of the present invention is exhibited by sucking during the period as described above. In addition, when the viscosity is 20 mPa · s or less, the coating liquid is more easily scattered, and therefore the production method of the present invention is more effective. In the production method of the present invention, when a coating liquid having a viscosity exceeding 50 mPa · s is used, the coating liquid formed between the other end 12b on the open side of the article 12 to be coated and the coating liquid surface 13a is used. Since the strength of the liquid film due to surface tension is high, the liquid film cannot be broken in the suction step, and the coating liquid itself is sucked, which may contaminate the inside of the coating object and the suction device. .

  The viscosity of the coating solution is a "vibrating viscometer" that controls the amplitude of the vibrator (sensitive plate) inserted into the sample and measures the drive current of the vibrator to determine the viscosity. "Capillary viscometer" that determines the viscosity from the pressure difference between the two ends of the tube, "Cylinder viscometer" that drops the cylindrical or spherical object in the sample and determines the viscosity from the time it falls for a certain distance, `` Rotary viscometer '' that inserts a conical rotor and measures its rotational torque to determine the viscosity, fills the sample with a fixed volume cup, and calculates the viscosity from the sample flow time from the pores below it It can be measured by a general viscometer such as a “cup viscometer”.

  Among these, the rotary viscometer and the vibration viscometer can be continuously measured, and the measurement data can be taken out with an electric signal.

  The measurement temperature is set to the temperature of the manufacturing conditions in the actual production line. In the case of the dip coating method as in the present invention, a range of approximately 15 ° C. to 30 ° C. is suitable, and the viscosity of the coating solution 13 only needs to be 50 mPa · s or less at the temperature of actual manufacturing conditions.

  The conductive substrate and photosensitive layer coating solution used in the production method of the present invention will be described below. The electrophotographic photoreceptor produced by the production method of the present invention includes a conductive substrate and a photosensitive layer. The photosensitive layer is obtained by applying a coating solution in which components of the photosensitive layer such as an organic functional material and a binder resin are dissolved or dispersed in a solvent on the conductive substrate with the dip coating apparatus 11 to a uniform thickness. The coating liquid layer is formed by drying.

  The electrophotographic photosensitive member produced by the production method of the present invention includes a laminated type electrophotographic photosensitive member and a single layer type electrophotographic photosensitive member. FIG. 4 is a cross-sectional view showing the configuration of the multilayer electrophotographic photosensitive member, and FIG. 5 is a cross-sectional view showing the configuration of the single-layer electrophotographic photosensitive member.

  In the multilayer electrophotographic photosensitive member as shown in FIG. 4, an undercoat layer 7 is provided on the outer peripheral surface of the conductive substrate 1, and a charge generation layer 5 and a charge transport layer 6 as the photosensitive layer 4 are further formed thereon. Are stacked in this order. In the single-layer electrophotographic photosensitive member as shown in FIG. 5, a subbing layer 7 is provided on the outer peripheral surface of the conductive substrate 1, and a single layer containing a charge transporting substance and a charge generating substance is further provided thereon. In this structure, the photosensitive layer 4 is laminated.

  As a material of the conductive substrate 1 that is an element tube for an electrophotographic photosensitive member, for example, a metal material such as aluminum, aluminum alloy, copper, zinc, stainless steel, titanium, or the like can be used. Also, without being limited to these metal materials, polymer materials such as polyethylene terephthalate, polyester, polyoxymethylene, and polystyrene, those obtained by laminating metal foil on the surface of hard paper or glass, and those obtained by vapor deposition of metal materials Alternatively, a conductive polymer, tin oxide, indium oxide, carbon particles, metal particles, or a conductive compound layer deposited or applied may be used. If necessary, the surface of the conductive substrate 1 is irregularly reflected within a range that does not affect the image quality, such as anodic oxide film treatment, surface treatment with chemicals or hot water, coloring treatment, or roughening the surface. Processing may be performed. In an electrophotographic process using a laser as an exposure light source, the wavelengths of the laser light are uniform, so that the incident laser light and the light reflected in the electrophotographic photosensitive member interfere with each other, and interference fringes due to this interference appear on the image. May cause image defects. By subjecting the surface of the conductive substrate to the irregular reflection treatment as described above, it is possible to prevent image defects due to interference of laser light having a uniform wavelength. As the shape of the conductive substrate 1, a cylindrical shape can be used in the present invention.

  An undercoat layer 7 may be provided on the outer peripheral surface of the conductive substrate 1. When there is no undercoat layer 7 between the conductive substrate 1 and the photosensitive layer 4, charges are injected from the conductive substrate 1 into the photosensitive layer 4, the charge potential is lowered, and the portion other than the portion that should be erased by exposure. The surface charge is reduced, and image defects such as fogging occur. In particular, when an image is formed using a reversal development process, a toner image is formed in a portion where the surface charge has decreased due to exposure. Therefore, if the surface charge decreases due to a factor other than exposure, the toner adheres to a white background and becomes minute. An image fogging called “black spot” in which black spots are formed occurs, resulting in significant image quality failure. That is, due to defects in the conductive substrate 1 or the photosensitive layer 4, the chargeability in a minute region is reduced, and image fogging such as black spots occurs, resulting in significant image defects.

  However, by providing the undercoat layer 7, it is possible to prevent the charge from being injected from the conductive substrate 1 to the photosensitive layer 4, so that the chargeability of the photosensitive layer 4 can be prevented from being lowered and should be erased by exposure. It is possible to suppress a decrease in surface charge other than the portion and prevent image defects such as fogging from occurring. In addition, since the undercoat layer 7 can cover defects on the surface of the conductive substrate 1 to obtain a uniform surface, the film formability of the photosensitive layer 4 can be improved. Further, peeling of the photosensitive layer 4 from the conductive substrate 1 can be suppressed, and adhesion between the conductive substrate 1 and the photosensitive layer 4 can be improved.

  For the undercoat layer 7, a resin layer or an alumite layer made of various resin materials is used. The resin material for forming the resin layer is polyethylene resin, polypropylene resin, polystyrene resin, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyurethane resin, epoxy resin, polyester resin, melamine resin, polycarbonate resin, polyester carbonate resin, polysulfone. Resin, phenoxy resin, polyarylate resin, silicone resin, polyvinyl butyral resin, polyamide resin and the like, copolymer resin containing two or more of repeating units constituting these resins, casein, gelatin, polyvinyl alcohol, Examples thereof include ethyl cellulose.

  The undercoat layer 7 may contain particles such as a metal oxide. By containing these particles, the volume resistance value of the undercoat layer 7 can be adjusted to further suppress the injection of charges from the conductive substrate 1 to the photosensitive layer 4, and electrophotographic photosensitive under various environments. The stability of the electrical properties of the body can be maintained. Examples of the metal oxide particles include titanium oxide, aluminum oxide, aluminum hydroxide, and tin oxide particles. When the undercoating layer 7 contains particles such as metal oxide, for example, a coating solution for forming an undercoating layer is prepared by dispersing these particles in a resin solution in which the above-described resin is dissolved. Can be formed on the conductive substrate 1 to form the undercoat layer 7.

  As the solvent for the resin solution, in addition to the organic solvent described above, alcohols such as water, methanol, ethanol and butanol, and glyme series such as methyl carbitol and butyl carbitol are also used. Moreover, the mixed solvent which mixed 2 or more types of these solvents can also be used.

  As a method for dispersing the aforementioned particles in the resin solution, a general method using a ball mill, a sand mill, an attritor, a vibration mill, an ultrasonic disperser, or the like can be used.

  The total content C of the resin and metal oxide in the coating solution for forming the undercoat layer is such that C / D is 1 / weight ratio with respect to the content D of the solvent used in the coating solution for forming the undercoat layer. It is preferable that it is 99-40 / 60, More preferably, it is 2 / 98-30 / 70. The ratio of resin to metal oxide (resin / metal oxide) is preferably 90/10 to 1/99 by weight, and more preferably 70/30 to 5/95.

  By adjusting the viscosity of the coating solution for forming the undercoat layer to be 50 mPa · s or less, the manufacturing method of the electrophotographic photosensitive member of the present invention can be applied, and defects due to scattering of the coating solution film may occur. And a uniform undercoat layer can be formed.

  The thickness of the undercoat layer 7 is preferably 0.01 μm or more and 20 μm or less, and more preferably 0.1 μm or more and 10 μm or less. If the thickness of the undercoat layer 7 is less than 0.01 μm, the undercoat layer 7 does not substantially function as the undercoat layer 7, and a uniform surface cannot be obtained by covering the defects of the conductive substrate 1. Since charge injection from 1 to the photosensitive layer 4 cannot be prevented, the chargeability of the photosensitive layer 4 is lowered. On the other hand, when the thickness of the undercoat layer 7 is larger than 20 μm, it is difficult to form the undercoat layer 7 uniformly, and the sensitivity characteristics are also deteriorated.

  The charge generation layer 5 contains, as a main component, a charge generation material that generates charges by absorbing light. Substances effective as a charge generating substance include azo pigments such as monoazo pigments, bisazo pigments, trisazo pigments, indigo pigments such as indigo or thioindigo, perylene pigments such as peryleneimide or perylene anhydride, anthraquinone or Polycyclic quinone pigments such as pyrenequinone, phthalocyanine pigments such as metal phthalocyanine or metal-free phthalocyanine, triphenylmethane dyes represented by methyl violet, crystal violet, knight blue, victoria blue, erythrosine, rhodamine B, rhodamine 3R Acridine dyes typified by acridine orange, frappeosin, thiazine dyes typified by methylene blue, methylene green, capri blue or meldra blue Oxazine dyes, squarylium dyes, pyrylium salts and thiopyrylium salts, thioindigo dyes, bisbenzimidazole dyes, quinacridone dyes, quinoline dyes, lake dyes, azo lake dyes, dioxazine dyes, azurenium dyes, Various organic pigments and dyes such as triallylmethane dyes, xanthene dyes, cyanine dyes, and inorganic such as amorphous silicon, amorphous selenium, tellurium, selenium-tellurium alloys, cadmium sulfide, antimony sulfide, zinc oxide, zinc sulfide Materials can be mentioned. These charge generating materials can be used alone or in combination of two or more.

  As a method for forming the charge generation layer 5, in the present invention, a coating solution for forming a charge generation layer obtained by dispersing a charge generation material in a solvent is formed on the conductive substrate 1 by the dip coating method described above.

  Examples of the binder resin include polyester resin, polystyrene resin, polyurethane resin, phenol resin, alkyd resin, melamine resin, epoxy resin, silicone resin, acrylic resin, methacrylic resin, polycarbonate resin, polyarylate resin, phenoxy resin, polyvinyl butyral resin, One type selected from the group consisting of resins such as polyvinyl formal resins, and copolymer resins containing two or more of the repeating units constituting these resins, or a mixture of two or more types is used. Is done. Specific examples of the copolymer resin include insulating resins such as vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, and acrylonitrile-styrene copolymer resin. be able to. The binder resin is not limited to those described above, and a commonly used known resin can be used as the binder resin.

  Solvents include, for example, halogenated hydrocarbons such as tetrachloropropane or dichloroethane, ketones such as isophorone, methyl ethyl ketone, acetophenone, cyclohexanone, esters such as ethyl acetate, methyl benzoate, butyl acetate, tetrahydrofuran (THF), dioxane, dioxane. Ethers such as benzyl ether, 1,2-dimethoxyethane or dioxane, aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, tetralin, diphenylmethane, dimethoxybenzene and dichlorobenzene, sulfur-containing solvents such as diphenyl sulfide, Fluorine solvents such as hexafluoroisopropanol, aprotic polar solvents such as N, N-dimethylformamide or N, N-dimethylacetamide, etc. are used.Moreover, the solvent which mixed 2 or more types of these solvents can also be used.

  The mixing ratio of the charge generation material and the binder resin is preferably in the range of 10 wt% to 99 wt% of the charge generation material, assuming that the weight of the entire charge generation layer is 100%. If the charge generation material is less than 10% by weight, the sensitivity is insufficient. On the other hand, when the charge generation material exceeds 99% by weight, not only the film strength of the charge generation layer is decreased, but also the dispersibility of the charge generation material is decreased and coarse particles are increased. Since the surface charge is reduced, many image defects, particularly black spots, occur.

  As a pretreatment for dispersing the charge generation material in the binder resin solution, the charge generation material may be pulverized in advance by a pulverizer. Examples of the pulverizer used for the pulverization treatment include a ball mill, a sand mill, an attritor, a vibration mill, and an ultrasonic disperser.

  When the charge generating material is dispersed in the binder resin solution, examples of the disperser used include a paint shaker, a ball mill, and a sand mill. As a dispersion condition at this time, it is desirable to select an optimum condition so that impurities are not mixed due to wear of the container used and the members constituting the disperser.

  Furthermore, various additives such as a hole transport material, an electron transport material, an antioxidant, a dispersion stabilizer, and a sensitizer may be added to the charge generation layer 5 as necessary. As a result, the electrical characteristics are improved, and the storage stability as a coating liquid is also increased. Further, it is possible to reduce fatigue deterioration when the electrophotographic photosensitive member is repeatedly used, and to improve durability.

  The charge generation layer 5 is formed by preparing a coating solution for forming a charge generation layer as described above and applying the adjusted coating solution on the surface of an object to be coated by the production method of the present invention. The viscosity of the coating liquid for forming a charge generation layer used in the present invention is a coating liquid adjusted to be 50 mPa · s or less, and the coating liquid adjusted with this viscosity is used to produce the present invention. By the method, it is possible to form a high-quality charge generation layer 5 free from defects. The film thickness of the charge generation layer 5 is preferably 0.05 μm or more and 5.0 μm or less, and more preferably 0.1 μm or more and 1.0 μm or less. When the film thickness of the charge generation layer 5 is less than 0.05 μm, the light absorption efficiency is lowered, and the sensitivity is deteriorated due to the insufficient amount of charge generation. If the film thickness of the charge generation layer 5 exceeds 5.0 μm, a process in which excessive charge transfer inside the charge generation layer 5 erases the charge on the surface of the photoreceptor appears strongly, and the chargeability decreases.

  The charge transport layer 6 is obtained by incorporating a charge transport material having the ability to accept and transport the charges generated in the charge generation layer 5 into the binder resin. As the charge transport material, a hole transport material and an electron transport material can be used. Examples of hole transport materials include carbazole derivatives, pyrene derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, Polycyclic aromatic compounds, indole derivatives, pyrazoline derivatives, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, triarylmethane derivatives, phenylenediamine derivatives, stilbene Derivatives, enamine derivatives, benzidine derivatives and the like can be mentioned. Examples of the polymer having a group derived from these compounds in the main chain or side chain include poly-N-vinylcarbazole, poly-1-vinylpyrene, ethylcarbazole-formaldehyde resin, triphenylmethane polymer, and poly-9-vinyl. Anthracene or the like, or polysilane or the like can be given.

  Examples of electron transport materials include benzoquinone derivatives, tetracyanoethylene derivatives, tetracyanoquinodimethane derivatives, fluorenone derivatives, xanthone derivatives, phenanthraquinone derivatives, phthalic anhydride derivatives, diphenoquinone derivatives, and other organic compounds, amorphous silicon, amorphous Examples include inorganic materials such as selenium, tellurium, selenium-tellurium alloy, cadmium sulfide, antimony sulfide, zinc oxide, and zinc sulfide. The charge transport materials are not limited to those listed here, and can be used alone or in admixture of two or more.

As the binder resin for the charge transport layer 6, one having excellent compatibility with the charge transport material is selected. Specific examples include vinyl polymer resins such as polymethyl methacrylate resin, polystyrene resin, and polyvinyl chloride resin, and copolymer resins thereof, as well as polycarbonate resin, polyester resin, polyester carbonate resin, polysulfone resin, phenoxy resin, and epoxy. Examples thereof include resins such as resins, silicone resins, polyarylate resins, polyamide resins, methacrylic resins, acrylic resins, polyether resins, polyurethane resins, polyacrylamide resins, and phenol resins. Further, a thermosetting resin obtained by partially crosslinking these resins may be used. These resins may be used alone or in combination of two or more. Among the resins described above, polystyrene resin, polycarbonate resin, polyarylate resin or polyphenylene oxide has a volume resistance value of 10 ¹³ Ω or more and excellent electrical insulation, and also has excellent film formability and electrical characteristics. Therefore, it is particularly preferable to use these for the binder resin.

  The ratio (A / B) of the charge transport material (A) to the binder resin (B) is 10/12 to 10/30 by weight. When the ratio (A / B) is less than 10/30 and the ratio of the binder resin is increased, sufficient responsiveness cannot be obtained with the charge transport ability of the current charge transport material. On the other hand, when the ratio (A / B) exceeds 10/12 and the binder resin ratio decreases, the printing durability decreases and the wear amount of the photosensitive layer 4 increases. Therefore, the ratio (A / B) is set to 10/12 or more and 10/30 or less.

  In order to improve the film formability, flexibility and surface smoothness, the charge transport layer 6 may be mixed with an additive such as a plasticizer or a surface modifier as necessary. Examples of the plasticizer include biphenyl, biphenyl chloride, benzophenone, o-terphenyl, dibasic acid ester, fatty acid ester, phosphoric acid ester, phthalic acid ester, various fluorohydrocarbons, chlorinated paraffin, and epoxy type plasticizer. be able to. Examples of the surface modifier include silicone oil and fluororesin.

  The charge transport layer 6 may be added with fine particles of an inorganic compound or an organic compound in order to increase the mechanical strength and improve the electrical characteristics. Further, an antioxidant and a sensitizer are added as necessary. Various additives such as an agent may be added. As a result, potential characteristics are improved, storage stability as a coating liquid is increased, fatigue deterioration when an electrophotographic photosensitive member is repeatedly used can be reduced, and durability can be improved.

  As the antioxidant, a hindered phenol derivative or a hindered amine derivative is preferably used. The hindered phenol derivative is preferably used in the range of 0.1% by weight to 50% by weight with respect to the charge transport material. The hindered amine derivative is preferably used in the range of 0.1 wt% to 50 wt% with respect to the charge transport material. Moreover, a hindered phenol derivative and a hindered amine derivative may be mixed and used. In this case, it is preferable that the total use amount of the hindered phenol derivative and the hindered amine derivative is in the range of 0.1 wt% to 50 wt% with respect to the charge transport material. When the amount of hindered phenol derivative used, the amount of hindered amine derivative used, or the total amount of hindered phenol derivative and hindered amine derivative used is less than 0.1% by weight based on the charge transport material, the storage stability of the coating solution is improved. It is not possible to exhibit a sufficient effect for improvement and durability improvement of the electrophotographic photosensitive member. If it exceeds 50% by weight, the sensitivity characteristics are adversely affected.

  Solvents used in the coating solution for forming the charge transport layer include aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, tetralin, diphenylmethane, dimethoxybenzene, dichlorobenzene, halogenated hydrocarbons such as dichloromethane or dichloroethane, THF , Ethers such as dioxane, dibenzyl ether, dimethoxymethyl ether, ketones such as cyclohexanone, acetophenone, isophorone, esters such as methyl benzoate or ethyl acetate, sulfur-containing solvents such as diphenyl sulfide, hexafluoroisopropanol, etc. One kind selected from the group consisting of an aprotic polar solvent such as a fluorine-based solvent and N, N-dimethylformamide can be used alone or in admixture of two or more. Further, a solvent such as alcohols, acetonitrile or methyl ethyl ketone can be further added to the above-described solvent as necessary.

  The film thickness of the charge transport layer 6 is preferably 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 40 μm or less. When the film thickness of the charge transport layer 6 is less than 5 μm, the charge holding ability on the surface of the electrophotographic photosensitive member is lowered. On the other hand, when the thickness of the charge transport layer 6 exceeds 50 μm, the resolution of the electrophotographic photosensitive member decreases. Accordingly, the thickness is set to 5 μm or more and 50 μm or less.

  If necessary, a surface protective layer may be provided to protect the surface of the photosensitive layer 4. For the surface protective layer, a thermoplastic resin, light, or a mature curable resin can be used.

Examples of the present invention will be described below, but the present invention is not limited thereto.
Example 1
60 parts by weight of titanium oxide (manufactured by Showa Denko KK: TS-043 [titanium oxide 90 wt%, anhydrous silicon dioxide 10 wt%]) as metal oxide fine particles, Al ₂ O ₃ as another type of metal oxide fine particles, Titanium oxide treated with SiO ₂ · nH ₂ O (manufactured by Teika: MT-500SA [titanium oxide 90 wt%, Al (OH) ₃ 5 wt%, SiO ₂ .nH ₂ O 5 wt%]) 60 parts by weight 30 parts by weight of a polyamide resin (manufactured by Daicel Degussa Co., Ltd .: X1010) as a binder resin and a mixed solvent of 276 parts by weight of methanol, 553 parts by weight of tetrahydrofuran and 92 parts by weight of n-propanol as a solvent are put into a stirring tank of a horizontal bead mill The horizontal bead mill body with a capacity of 16500 ml contains 80% silicon nitride beads with a diameter of 0.5 mm as the dispersion medium. Up to a volume amount of. Then, the solution was fed from the stirring tank to the disperser main body via a diaphragm pump and dispersed while circulating for 15 hours to prepare 64000 ml of an undercoat layer forming coating solution having a solid content concentration of 14.0% by weight.

  This undercoat layer coating solution was dip-coated using the dip coating apparatus 11 shown in FIG. The viscosity of the coating solution for forming the undercoat layer at the time of application was 12.6 mPa · s. In addition, the dip coating apparatus 11 used in the present example has an interval d between adjacent coated objects of 45 mm and can process 40 coated objects at a time. 70 mm. In coating, an aluminum conductive substrate having an inner diameter of 28.5 mm, a wall thickness of 0.75 mm, and a total length of 340 mm is used as the conductive substrate, and the coating solution for the dip coating apparatus 11 in which the coating solution for forming the undercoat layer is contained. The bath was immersed in the bath until the upper end of the conductive substrate remained at 1 mm, stopped for 5 seconds, and pulled up at a constant speed of 2.0 mm / s. When pulling up, when the position of the open end of the conductive substrate becomes equal to the coating liquid level, the starting point of the period is the distance between the open end of the conductive substrate and the coating liquid level. Was 3.5 mm, a suction step of sucking air inside the conductive substrate for 0.5 seconds from the closed end of the conductive substrate was performed. In this way, the coating solution for forming the undercoat layer was applied to the surface of the conductive substrate and dried naturally to form an undercoat layer having a thickness of 1 μm. The same undercoat layer was formed for 25 pallets (10,000 in total).

  Next, in the X-ray diffraction spectrum by Cu-Kα characteristic X-ray (wavelength: 1.54Å) as oxotitanium phthalocyanine which is a charge generation material, a clear diffraction at least at a Bragg angle (2θ ± 0.2 degrees) of 27.2 degrees 2.3 parts by weight of oxotitanium phthalocyanine having a crystal structure showing a peak, 1.2 parts by weight of polyvinyl butyral resin (manufactured by Sekisui Chemical Co., Ltd .: ESREC BM-2), and 96.5 parts by weight of dimethoxyethane The mixture was mixed and dispersed with a paint shaker to prepare a coating solution for forming a charge generation layer having a solid concentration of 3.5% by weight. This charge generating layer forming coating solution was applied in the same dip coating apparatus 11 as described above. The viscosity at the time of application is 3.4 mPa · s. In coating, the conductive substrate on which the undercoat layer is formed is immersed in the coating solution from the other end on the open side with one end of the conductive substrate closed and the other end opened. The substrate was immersed until 1.2 mm of the upper end of the conductive substrate was left, stopped for 7 seconds, and pulled up at a constant speed of 2.3 mm / s. At the time of pulling up, when the position of the other end portion on the open side of the conductive substrate becomes equal to the coating liquid surface, the starting point is 2.5 mm from the starting point, that is, the open side end portion and the coating liquid surface When the distance “r” is 2.5 mm, a suction step of sucking air inside the conductive substrate from the one end portion on the closed side of the conductive substrate for 0.5 seconds was performed. After applying the charge generation layer forming coating solution as described above, it was naturally dried to form a charge generation layer having a thickness of 0.4 μm for 25 pallets (10,000 in total) on the undercoat layer.

Subsequently, 10 parts by weight of a hydrazone compound of the following structural formula (I) as a charge transport material, 16 parts by weight of a polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z400) as a binder resin, and dimethylpolysiloxane (Shin-Etsu Chemical) as a leveling agent Kogyo Co., Ltd .: KF-96) 0.0032 parts by weight, as an antioxidant (Sumitomo Chemical Co., Ltd .: Sumilizer BHT) 0.5 parts by weight is mixed with 106 parts by weight of tetrahydrofuran to obtain a solid concentration of 20% by weight, 20 A coating solution for forming a charge transport layer having a viscosity at 540 ° C. of 540 mPa · s was prepared. And it apply | coated on the said electric charge generation layer with the dip coating method, the hot air drying was performed at 120 degreeC for 1 hour, and the charge transport layer with a dry film thickness of 24 micrometers for 25 pallets (a total of 10000 pieces) was formed.
As described above, 10,000 electrophotographic photoreceptors of Example 1 were produced.

(Example 2)
An electrophotographic photoreceptor of Example 2 was produced in the same manner as in Example 1 except for the conditions for forming the undercoat layer.

  Using a mixed solvent of 452 parts by weight of methanol and 302 parts by weight of 1,3-dioxolane as the solvent for the coating solution for forming the undercoat layer, adjusting the coating solution for forming the undercoat layer with a solid content concentration of 16.6% by weight The undercoat layer was formed on the conductive substrate by pulling up at a constant speed of 1.4 mm / s. As a suction step when pulling up, when the position of the other end portion on the open side of the conductive substrate becomes equal to the coating liquid surface, when starting up 7.0 mm from the start point, that is, with the open side end portion Suction was performed for 4 seconds when the distance r from the coating liquid surface was 7.0 mm.

  The viscosity of the coating solution for forming the undercoat layer at the time of coating was 49.9 mPa · s. The connection length due to the surface tension of the coating liquid between the other end on the open side of the coating object and the coating liquid surface during the formation of the undercoat layer was approximately 8.2 mm.

  Here, the connection length refers to the connection due to the surface tension between the opening side end and the coating liquid surface without performing the suction operation when the opening side end moves away from the coating liquid surface in the pulling process. The distance between the coating liquid surface and the opening-side end when it is naturally cut corresponds to the maximum length of connection due to surface tension.

  In this example, a dip coating apparatus capable of applying 40 pieces at a time was used, and the connection length was the length when the connection was cut earliest among these 40 pieces.

(Example 3)
An electrophotographic photoreceptor of Example 3 was produced in the same manner as Example 1 except for the conditions for forming the undercoat layer.

  Using a mixed solvent of 259 parts by weight of methanol, 519 parts by weight of tetrahydrofuran and 86 parts by weight of n-propanol as a solvent for the coating liquid for forming the undercoat layer, a coating liquid for forming the undercoat layer having a solid content concentration of 14.8% by weight was prepared. Then, the substrate was pulled up at a constant speed of 1.8 mm / s to form an undercoat layer on the conductive substrate. As a suction process when pulling up, when the position of the other end portion on the open side of the conductive substrate becomes equal to the coating liquid surface, when it is lifted 5.3 mm from the start point, that is, with the open side end portion When the distance r from the coating liquid surface was 5.3 mm, suction was performed for 1.3 seconds. The viscosity of the coating solution for forming the undercoat layer at the time of application was 19.7 mPa · s. The connection length due to the surface tension of the coating liquid between the other end on the open side of the coating object and the coating liquid surface during the formation of the undercoat layer was approximately 6.1 mm.

Example 4
As a suction process at the time of pulling, Example 2 except that the suction was performed for 4.0 seconds from the start point, that is, when the distance r between the open side end portion and the coating liquid surface was 4.0 mm. Similarly, an electrophotographic photoreceptor of Example 4 was produced.

(Example 5)
A charge generation coating solution was prepared by using 134 parts by weight of 1,3-dioxolane as a solvent for the charge generation layer formation solution, and was pulled up at a pulling rate of 4.8 mm / s on the surface of the conductive substrate on which the undercoat layer was formed. When the charge generation layer forming coating solution is applied and further lifted by 5.0 mm from the starting point in the suction step when forming the charge generation layer, that is, the distance r between the other end on the open side and the coating solution surface is 5. The electrophotographic photosensitive member of Example 5 was the same as Example 1 except that the pulling up of the conductive substrate was interrupted for 5 seconds when it reached 0 mm, and suction was performed for 0.5 seconds after 3 seconds had elapsed from the start of the interruption. Was made. The coating solution for forming a charge generation layer had a solid content concentration of 2.55% by weight and a viscosity at the time of coating of 1.70 mPa · s.

(Example 6)
An electrophotographic photoreceptor of Example 6 was produced in the same manner as in Example 5 except that the interruption time for interrupting the pulling of the conductive substrate was 12 seconds.

(Comparative Example 1)
An electrophotographic photoreceptor of Comparative Example 1 was produced in the same manner as in Example 1 except that the suction step was not performed when the undercoat layer was formed and when the charge generation layer was formed.

(Comparative Example 2)
As a suction step when forming the undercoat layer, suction was performed when the starting point was pulled up by 15.0 mm, that is, when the distance r between the open end and the coating liquid surface was 15.0 mm. Further, as a suction step when forming the charge generation layer, suction was performed when the position was raised 12.0 mm from the starting point, that is, when the distance r between the open end and the coating liquid surface was 12.0 mm.

  In each of the above suction steps, when the suction is started, the connection due to the surface tension of the coating liquid between the open-side end portion of the coating object and the coating liquid surface has already been completely broken. An electrophotographic photosensitive member of Comparative Example 2 was produced in the same manner as in Example 1 except for these suction steps.

(Comparative Example 3)
Using a mixed solvent of 215 parts by weight of methanol, 430 parts by weight of tetrahydrofuran and 72 parts by weight of n-propanol as a solvent for the coating liquid for forming the undercoat layer, a coating solution for forming the undercoat layer having a solid content of 17.3% by weight is prepared. Then, the film was pulled up at a constant speed of 1.0 mm / s. The viscosity of the coating solution for forming the undercoat layer at the time of application was 69.6 mPa · s. As a suction process at the time of pulling up, the suction was performed when the start point was pulled up by 4.0 mm, that is, when the distance r between the open end and the coating liquid surface was 4.0 mm.

  Under such conditions, in the suction process, a large amount of the undercoat layer forming coating solution is sucked into the conductive substrate and contaminated up to the gripping means in the conductive substrate. Canceled.

  Visual inspection was performed on the electrophotographic photoreceptors of Examples and Comparative Examples produced as described above. Whether or not droplets of the coating liquid for forming the undercoat layer are attached (defective item name: UC liquid skip), or whether the droplets of the coating liquid for forming the charge generation layer are adhered (defective item name: CG liquid skip). Judgment was made, and the occurrence rate of defects due to adhesion of each coating liquid was calculated and evaluated.

  The electrophotographic photosensitive members produced in Example 5 and Comparative Example 4 were each mounted on a digital copier MX-M503N manufactured by Sharp Corporation, and a halftone image was obtained from a connected computer. Data was sent to a copier and output in printer mode for image evaluation.

  The suction conditions, visual observation results, and image evaluation results of the electrophotographic photoreceptors produced in the above Examples and Comparative Examples are summarized in Table 1 below.

  As shown in Table 1, in Comparative Example 1 in which suction was not performed, and in Comparative Example 2 in which suction was performed after the connection between the open-side end portion of the conductive substrate and the coating liquid surface was broken, the UC liquid was skipped. As a result, the defect rate due to CG liquid jumping was high. In addition, since these two comparative examples had similar defect rate values, the suction performed at the timing performed in Comparative Example 2 has no effect on the improvement of the UC liquid jump and the CG liquid jump defect. Is shown.

  In the comparative example 3, since the coating liquid for forming the undercoat layer having a viscosity exceeding 50 mPa · s was used, the inside of the conductive substrate was contaminated by sucking the coating liquid.

  On the other hand, in Examples 1 to 4, the occurrence of liquid skipping defects was very small in both the undercoat layer and the charge generation layer, and the viscosity was low as in the undercoat layer forming coating solution and the charge generating layer forming coating solution. Even when the coating liquid is used, it is clear that the suction process of the present invention works effectively and suppresses the occurrence of defects due to liquid skipping.

  In Example 5, since the coating speed is more than double that of Example 1, the period during which the other end on the open side of the object to be coated is connected to the coating liquid surface is shortened, resulting in a large load on suction control. However, it is possible to stably perform suction by interrupting the lifting of the object to be coated before the suction is performed, and even if the lifting is interrupted, the coating for forming the charge generation layer is possible. Since the exposure time to the solvent vapor of the liquid was short, the film thickness of the charge generation layer was not affected in the vicinity of the other end of the coated object, and the image evaluation was good.

  Further, in Example 6 in which the pull-up was interrupted for 12 seconds after the other end on the open side of the object to be applied reached the coating liquid level, the interrupt time was long, and the other end on the open side of the conductive substrate generated charge. Since the layer forming coating solution was too exposed to the solvent vapor, the film thickness of the charge generating layer forming coating solution adhering to the other end became thin. This caused a slight decrease in image density due to insufficient sensitivity near the other end of the conductive substrate, which was not the best image quality. A sufficient improvement effect was observed, and no traces of various liquids were observed on the formed image.

  From the above evaluation results, it was found that the production method of the present invention can produce a high-quality electrophotographic photosensitive member by suppressing scattering of the coating solution even when a coating solution having a low viscosity is used.

DESCRIPTION OF SYMBOLS 1 Conductive substrate 4 Photosensitive layer 5 Charge generation layer 6 Charge transport layer 7 Undercoat layer 11 Immersion coating device 12 Coating object 13 Coating liquid 13a Coating liquid surface 14 Coating liquid tank 15 Gripping device 16 Lifting device 31 Stirring tank 39 Coating layer

Claims (5)

A dipping step of immersing the cylindrical substrate in a coating solution having a viscosity of 50 mPa · s or less from the opened other end side in a state where one end is closed and the other end is opened;
A forming step of forming a coating layer made of the coating solution on the outer peripheral surface of the substrate by pulling up the immersed substrate from the coating solution, wherein the other end of the substrate is above the liquid level of the coating solution. A step of sucking air inside the substrate from the closed one end side within a period in which the other end of the substrate is in contact with a part of the coating solution due to the surface tension of the coating solution. A method for producing an electrophotographic photosensitive member.   The method for producing an electrophotographic photosensitive member according to claim 1, wherein the coating solution has a viscosity of 20 mPa · s or less.   3. The method of manufacturing an electrophotographic photosensitive member according to claim 1, wherein the period of the forming step is a period in which the distance between the other end of the substrate and the liquid surface of the coating solution is 0 to 5 mm.   The electrophotographic photosensitive member according to claim 1, wherein during the period of the forming step, the pulling of the substrate is interrupted for 1 to 10 seconds, and the suction is performed during the interruption. Production method. A cylindrical substrate;
An electrophotographic layer comprising: a photosensitive layer obtained by drying a coating layer formed on an outer peripheral surface of a substrate by the method for producing an electrophotographic photosensitive member according to claim 1. Photoconductor.